1. Field of the Invention
The present invention relates to catheter systems for delivery of medical devices into a patient, and particularly to medical devices that are delivered to a treatment site using a guidewire.
2. Description of Related Art
Minimally invasive (or “interventional”) medical procedures are commonly employed today to avoid the substantial effort and trauma inherent in traditional surgery. Instead of directly accessing a treatment site through surgical procedures, a physician will make a small incision into a remote vessel (e.g., a femoral artery) and guide the necessary tools to the treatment site using fluoroscopy or other visualization techniques. Access to the treatment site is first achieved using very low profile devices that can be “steered” through the various branches of vessels to the correct treatment location. Typically these initial small diameter devices will be a steerable guidewire or a small-diameter guiding catheter that is followed by insertion of a guidewire. Once in the correct position, treatment devices can then be attached to the guidewire and advanced to the treatment site along the guidewire like a train traveling along a track. Following treatment, each treatment device is then pulled out of the patient along the same guidewire to allow, if needed, further treatment devices to be advanced along the guidewire to the treatment site.
This basic approach is now used in a wide variety of medical procedures, including internal vessel repairs (e.g., repairing aneurysms in the aorta or other vessels using grafts or stent-graft devices) and treating blockages in vessels (e.g., performing balloon angioplasty or thrombectomy, and stent or stent-graft placements). All of these procedures tend to be much faster and far less traumatic than comparable surgical treatments. As a result, there are a host of benefits by using these procedures, including: fewer medical professionals need to attend the procedures; the procedures can be completed more rapidly; the patient may need far less extensive anesthesia and, where appropriate, can be awake and cooperative during the procedure; and since the trauma of open surgery is avoided overall hospital stays are dramatically reduced (e.g., for the repair of an abdominal aortic aneurysm hospital stays can be reduced from over a week including intensive care to only a couple of days or less).
Two basic categories of techniques are commonly used today to advance treatment apparatus to a treatment site along a guidewire. First, “over the wire” (OTW) techniques employ a long guidewire that extends far out of the patient's body. In the OTW procedures, each treatment device is mounted on a catheter that includes a guidewire lumen extending the entire length of the catheter. The physician threads each catheter completely over the length of the guidewire extending out of the patient and, while an assistant controls the tail end of the guidewire, the physician feeds the catheter to the treatment site. Following treatment, the entire catheter is then removed along the guidewire, again with the assistant controlling the tail end of the guidewire to keep it from moving out of position or touching the floor or other non-sterile areas. The OTW techniques have been widely practiced and provide very good trackability for the devices along the guidewire. However, these techniques require that the long tail end of the guidewire be controlled at all times, requiring at least one additional assistant throughout the procedure. Further, the threading of the entire length of the catheter along the guidewire can be somewhat difficult and time consuming. Moreover, limiting the speed with which procedures can be completed and the types of procedures that can be easily performed, these techniques require each treatment device to be completely retracted along the guidewire before a further treatment device can be advanced along the same guidewire to the treatment site.
The second common category of techniques for advancing treatment apparatus to a treatment site is commonly referred to as “rapid exchange” techniques. In rapid exchange procedures a guidewire lumen is provided over only a relatively short distal length of the treatment catheter, having a guidewire port exiting the catheter shaft next to or a short distance back from the treatment device. In this manner a relatively short guidewire can be employed that does not extend far from the patient's body. The physician advances the catheter over the guidewire (through the guidewire lumen) and gains control of the proximal end of the guidewire where it exits the catheter near the catheter's distal end. The physician can then guide the catheter into position without the need of an assistant controlling an extra long guidewire tail. Examples of such devices are described in U.S. Pat. Nos. 4,762,129 to Bonzel and 5,040,548 to Yock. Although the rapid exchange techniques may sacrifice some trackability in use, these techniques can allow for faster threading of each treatment device and cost savings in the elimination of extra long guidewires and one assistant to control the guidewire tail during the procedure. However, in practice these techniques also require each treatment device to be completely retracted along the guidewire before a further treatment implement can be advanced along the guidewire to the treatment site.
Other apparatus have been developed to provide some of the same benefits provided by the rapid exchange catheter techniques. For example, it has been suggested that the guidewire connect to the treatment catheter only at the distal tip of the guidewire, with a tube housing a guidewire lumen extending along the outside of the treatment device. Examples of these devices are described in U.S. Pat. Nos. 5,458,639 to Tsukashima et al. and 6,371,961 to Osborne et al. A similar device is taught in U.S. Pat. No. 6,394,995 to Solar et al. whereby an “advancement member” is provided attached to a treatment balloon; the advancement member includes a short tube at its far distal end forming a guidewire lumen. While these devices may deliver some of the same benefits of the conventional rapid exchange catheters, trackability may be a far greater problem since the guidewire is attached to the treatment catheter only at the very tip of the catheter. Additionally, depending upon the dimensions and stiffness of the tube housing the guidewire lumen (or, in the case of the Solar et al. device, of the “advancement member”), its presence on the outside of the treatment device may interfere with the proper operation of the treatment device. Finally, as was true with the other techniques discussed above, these devices would appear to require each treatment device to be completely retracted along the guidewire before a further treatment implement can be advanced along the guidewire to the treatment site.
It is accordingly a purpose of the present invention to provide an improved apparatus for advancement of a catheter along a guidewire that can be loaded and operated on a relatively short guidewire by a single operator.
It is a further purpose of the present invention for such an apparatus to provide a guidewire lumen that affords all necessary trackability while a treatment device is being advanced to a treatment site.
It is still a further purpose of the present invention for such an apparatus to allow other treatment devices to be advanced along the same guidewire without prior removal of the first treatment device.
These and other purposes of the present invention will become evident from review of the following description.